Match Likelihood Ratio for Uncertain Genotypes

Abstract: Genetic data are not necessarily fully informative, leading to uncertainty in an inferred genotype.
The posterior genotype probability distribution incorporates the identification information
present in the data. To compare uncertain genotypes, we introduce here a match likelihood ratio
(MLR), a simple generalization of the likelihood ratio standardly used to understand the import
of genetic evidence in forensic applications. The MLR gives the relative probability of a match
between questioned evidence and a suspect, with respect to a match between the evidence and a
relevant population. Coancestry can be naturally incorporated. We present illustrative
examples, and provide a detailed analysis and comparison for a two person DNA mixture. We
describe MLR's computation efficiencies when making multiple genotype comparisons, and
show how MLR was used to explain evidence in court. As statistical computing of forensic
DNA inferences becomes more commonplace, the MLR may help in quantifying match
identification information.